Lab Tech Flashcards
The following will cause drift errors in an analytical balance EXCEPT
A. Balance door is open.
B. Balance is not levelled
C. Air currents are present in the laboratory.
D. Temperature of the balance and the sample to be weighed is the same.
D
Objects cannot be weighed when hot or warm. But if you were to take a sample out and wait for it to cool it would pick up moisture so it should be placed in a/an/at
A. oven
B. desiccator
C. room temp
D. fume hood
B
It is the nominal volume of water (or mercury) contained, or delivered by an article of volumetric glassware, at its reference temperature.
A. accuracy
B. calibration
C. capacity
D. measurand
C
A student is tasked to measure 12 mL of a liquid as precisely as possible. Which measuring device should be selected for this task?
A. 25 mL beaker
B. 25 mL graduated cylinder
C. 25 mL conical flask
D. 25 mL volumetric flask
B
Which of the following is TRUE about TC pipets?
A. TC means “to carry”.
B. It commonly does not have a colored band.
C. It is used if the liquid left in the pipet is already accounted.
D. None of the above.
D
A student needs to transfer his precipitant from the beaker to the filter paper. Which of the following would be the best procedure in order to ensure a quantitative transfer of the precipitate?
A. Most of the supernatant liquid is decanted then bulk of precipitate is transferred to filter paper through a stirring rod, then the beaker is washed with large volumes of wash solution.
B. Most of the supernatant liquid decanted first, then bulk of the precipitate is transferred through a stirring rod. The beaker is washed several times with small volumes of wash solution.
C. Solution is shaken, then immediately filtered; beaker is washed with big volumes of wash solution.
D. None of the above.
A
To determine the density of a liquid, which of the follewing should be used?
A. graduated cylinder
B. volumetric flask
C. pycnometer
D. pipette
C
Which is TRUE for a 19/22 stopper?
A. radius =19 mm, height = 22 mm
B. radius = 22 mm, height = 19 mm
C. diameter = 19 mm, height = 22 mm
D. diameter = 22 mm, height = 19 mm
C
Which technique is recommended for determining the odor of an unknown liquid in the laboratory?
A. Hold a test tube of the liquid under the nose and inhale the vapor.
B. Transfer a few drops of the liquid to the bench top and inhale the vapor from there.
C. Use a dropper to collect a small quantity of the vapor and squirt this under the nose while inhaling.
D. Use a hand to fan some of the vapor from the test tube to the nose and inhale.
D
The size of the sample taken for analysis depends on the ________
A. concentration of analyte
B. equipment to be used
C. specific chemical tests
D. all of the above
D
Possible sources of contamination during sample preparation include
A. reagents
B. glassware from previous experiment
C. equipment from previous experiment
D. all of the above
D
Which of the following can cause errors during the sample preparation?
I. Loss of sample during weighing or dissolution.
Il. Contamination by impurities in reagents and in the environment.
Ill. Changes in mass due to varying humidity and temperature.
IV. Obtaining nonhomogeneous sample from the bulk.
A. I and II only
B. I, III, and IV
C. I, II, and III
D. I, II, IlI, and IV
D
Method of passing the sample through a metal or plastic mesh of a uniform cross-sectional area to separate particles into uniform sizes.
A. sieving
B. milling
C. pulverizing
D. macerating
A
Which of the following can remove a fairly large amount of water from a sample that contains thermally labile material?
A. hotplate
B. freeze dryer
C. convection oven
D. microwave equipment
B
Sample preparation technique used prior to instrumental analysis of metals.
A. sieving
B. clean-up
C. acid digestion
D. liquid-liquid extraction
C
